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973-c. 1050

Arab Mathematician, Astronomer, and Geographer

Al-Biruni, sometimes referred to as Abu Rayhan al-Biruni, conducted a great deal of original mathematical and astronomical work, most notably when he collaborated with Abu al-Wafa (940-998) on determining the longitudinal difference between Baghdad and his city of Kath in what is now Uzbekistan. He also served an important function as a transmitter of ideas from India, where he spent part of his career, to the Arab world. In all, al-Biruni published well over 100 works.

Born near Kath in the town of Khwarizm on September 4, 973, al-Biruni gained an early education in astronomy and mathematics from Abu Nasr Mansur, whose family ruled the region at that time. As a youngster, he made astronomical observations using a meridian ring.

His world at Kath was soon shattered when in 995 the ruler of nearby Jurjaniya invaded. Al-Biruni most likely fled to the town of Rayy. There he met the astronomer al-Khujandi, with whom he discussed the latter's observations made using a mural sextant. Later al-Biruni would write on this subject in his Tahdid.

By 997, al-Biruni was back in Kath, where he observed a lunar eclipse. As it happened, Abu al-Wafa had observed the same eclipse from Baghdad, and by comparing the difference in time between the two readings, the two scientists were able to determine the longitudinal difference between the two cities. Not only was this a remarkable example of scientific collaboration in an era that lacked electronic communication or easy travel, the findings of al-Biruni and Abu al-Wafa represented one of the few instances in which accurate longitudinal calculations were made in the premodern period.

During the years that followed, al-Biruni traveled extensively in Muslim central Asia, collecting information he would use in his monumental history of the region. The latter, known in English simply as the Chronology, appeared in 1000, and is one of the most useful sources available for information on Iranian calendars and local history.

Al-Biruni became a leading member of the court at Jurjaniya beginning in 1004, and conducted many of his astronomical observations during the period that followed. But in 1017, he was confronted with the same sort of political turmoil that had marred his youth: in that year, Sultan Mahmud of Ghazni (r. 997-1030), brother-in-law to the shah of Jurjaniya, invaded and kidnapped al-Biruni.

The scientist made the best of his captivity, and after Mahmud sent him to Kabul in 1018, he began making astronomical observations there. Mahmud also provided him with his introduction to India, a land the sultan invaded in 1022 and again in 1026. As a result, al-Biruni had the opportunity to learn Sanskrit and collected information on Hindu astronomy and astrology.

It was during this period that al-Biruni wrote many of his works, including On Shadows (c. 1021), Tahdid (1025), and On Chords (1027), which along with other writings provided an invaluable history of both Hindu and Muslim advances in astronomy during the period from the eighth to tenth centuries. In later years he wrote on subjects that included specific gravity, gemology, pharmacology, and—in the Tahfim—astrology. He died in about 1050 in Afghanistan.